Friends of mine did Buggyfit or something similar - not sure if they allow older kids though.
Walk everywhere, ban yourself from using the car on two or three weekdays, come rain or shine - I've been doing this (more or less) and a good few pounds have come off and my fitness levels seem better for it.
You could try pockets of 10 mins exercise when you gte a chance. Theres some workout vids about called 10 min trainer that you could check out. Or skipping - skipping is v effective cardio and handy as anything
I recommend Jillian Michaels 30 Day Shred (£5). Its a 20 min work out in 3 levels, you do each for 10 days. You can do it every other day, build it up, its short but hard. You do it with weights so you can up those as you get stronger. Very effective.
Also get a skipping rope, do 10 mins skipping 5 mins exercises, then another 10 mins skipping. Aim for 20 mins a day of exercise and you'll be losing steadily and regaining fitness. PLus can do it at home when kiddies sleeping etc. Or start running, pop out in the morning before your partner leaves and build up to a quick 20 min run.
I'd also recommend some sort of online calorie counting tool - I use my fitness pal which is brilliant. Often losing weight is really just a matter of a really moderate cal deficit (200-300 cals so eating about 1500-1700 is low enough to lose weight at a steady clip) thats very achievable. Without this kind of calorie counting I often over restrict what Im eating, eat too little (1000-1200 is just too little for me), then binge for a couple of days and gain weight - esp if tired and busy with kids
After dd I gained quite a lot of weight and having just had ds I want to avoid falling into the same trap.
I know I gained weight after dd because I was so sleep deprived at the 4-6 month mark that I just lived off sugar, crap, rubbish and junk. I can already feel the sugar cravings kicking off with ds but I'm in a better position to eat healthily now (due to range of shops in our new area) and know to avoid sweets, chocolate, crisps, ice cream and more chocolate sugar.
I lost all that gained weight whilst pg (morning sickness) and I'm back to a good weight now just after the birth. I'm really, really keen not to gain any weight now.
So eating well is one thing But actually getting fit has me stumped. Dd is just under 2, I don't have the childcare to go anywhere solo, DH works long hours... So what's the best way to get fit with two little ones in my situation?